FEATURE REQUEST: Add more dynamics/options for toc element

[samjco]

More options like:
-Option to Highlight text when the element is in view.
-Move the TOC section as a vertical slider for links if more links show past a certain threshold.
-Option to change the type from <button> to <li> or any element.

Here are some example sites:
http://gregfranko.com/jquery.tocify.js/
https://tscanlin.github.io/tocbot/